It has been known for a long time to define a chamber, within containers, such as cans, by means of an elastomeric formation, which latter communicates through a delivery opening with a delivery valve. The inherent elasticity of the elastomeric material of a synthetic or natural elastomer is utilized in order to put the filling material forced into the chamber under pressure so that it can be delivered by pressure from the valve.
Such cans or tubular formations of elastomeric material of the above-mentioned type are known in very different embodiments, as e.g. from:
U.S. Pat. Nos. 3,791,557, 4,121,737, 3,083,871, 4,222,499 British Patent 1,463,336 U.S. Pat. Nos. 3,738,538 3,672,543, 3,876,115, 2,816,690, 3,698,595, 3,940,026.
Although a multiplicity of proposals are known for providing cans with such a sock as a pressure-producing element, these techniques have in the past been seldom employed. This has been true although actually the advantage is obtained that no separate propulsion gas needs to be introduced, either in the filling substance itself or, in two-chamber cans, in a chamber between a can housing and the inner chamber receiving the filling substance. The problems which arise with cans or tubular formations of the initially-mentioned type are as follows:
When filling of the filling substance under pressure in order to expand the tubular formation provided, the expansion of the formation is scarcely controlled, so the elastomeric formation can expand more at certain parts than at others and consequently such parts are overstressed.
Upon emptying of the said formation, there remains an amount of filling substance which previously could be determined only with difficulty, which could not be predetermined, sometimes because of the above-mentioned difficult control of the formation expansion ratios during the filling of the substance under pressure.